Conventionally, JP-2003-269023A for example, proposes a vehicle equipment control system. The system has an auto-lock function for automatically locking vehicle doors when a user leaves a vehicle. In the system, the distance permitting auto-locking is specifiable. When a “short distance” is specified, then the auto-lock function is executed upon the condition where LF (low frequency) communication from the vehicle device to the portable unit becomes disabled. On the other hand, when a “long distance” is specified, the auto-lock function is executed upon the condition where UHF (ultra high frequency) communication from the portable unit to the vehicle device becomes disabled.
Further, JP-10-59131A proposes another door locking system. In this door locking system, an operation of a switch provided in a respective door knob of a vehicle is set as a trigger, and two-way communication between an in-vehicle device and a portable transmitter-receiver device (portable unit) is performed in response to that operation. In the event that a normal response signal has been received from the portable unit, a corresponding door of the vehicle is locked through the vehicle device. In this system, when locking the door, a low output verification signal and a high output verification signal are output from the in-vehicle device, thereby to prevent the portable unit from being forgotten in the vehicle compartment. More specifically, the system can be preset such that a receivable range of low output verification signals in the portable unit is substantially the same as those in the compartment. As such, in the event that a response to the low output verification signal has been received, then it can be determined that the portable unit is forgotten in the compartment.
Alternatively, when no response to the low output verification signal has been received, then the high output verification signal is succeedingly transmitted to verify the existence of the response from the portable unit. The receivable range of the high output verification signals is preset to include a predetermined range covering the vicinity of the vehicle. As such, when the response to the high output verification has been received from the portable unit, then it is determined that the user of the portable unit is present in the outside of the vehicle, and hence door is locked.
As described above, the vehicle door locking systems include auto-lock and trigger lock systems. The auto-lock system locks the respective vehicle door automatically upon leaving of the user from the vehicle. The trigger lock system operates in response to a trigger set to the user operation performed on a switch provided in a vehicle door.
In order to improve usability of such systems for users, it is preferable that the vehicle door is lockable by any one of the auto-lock and trigger lock systems. In this case, in the event that the user gets off the vehicle and moves away without operating the switch provided in the vehicle door, the door is locked by the auto-lock system. Alternatively, in the event that the user has operated the switch provided in the vehicle door, the vehicle door is locked by the trigger lock system.
However, in the case that the vehicle door lockable by using any one of the auto-lock and trigger lock systems, such drawbacks as described below may arise.
It is preferable that, as described in JP-10-59131A, in order to prevent the portable unit from being forgotten and confined in the compartment, when locking the vehicle door, an inside transmitter for transmitting request signal towards a vehicle compartment is used to verify whether the portable unit is present in the compartment. However, this approach encounters difficulty in setting a transmission range of the request signal of the inside transmitter to include the overall area in the compartment into a communication area that enables communication with the portable unit. This is because, when the transmitting range of the request signal is set in such the manner, the transmitting wave of the request signal leaks from a window of the respective vehicle door.
When operating a switch of a vehicle door to lock the vehicle door, a user is located relatively close to the vehicle. As such, when the transmission wave of the request signal has leaked, the portable unit carried by the user may react with the leaking request signal and can return a response signal. Consequently, while the user is carrying the portable unit, an alarm indicating that the portable unit has been forgotten in the compartment occurs and the vehicle door cannot be locked.
In order to overcome such drawbacks, it is contemplated that when operating the switch of the vehicle door, the user reduces the transmission output level to an extent not causing the reaction of the portable unit. In this case, however, in the compartment, there occurs a dead zone area that disables the communication between the inside transmitter and the portable unit. As such, in the event that, while the portable unit is placed in the dead zone area, the user gets out of the vehicle and executes the auto-lock function under the condition where the two-way communication with the inside transmitter is disabled, the portable unit is undesirably confined in the compartment. Alternatively, suppose that the auto-lock function has been executed under the condition where, as described in JP-2003-269023A, the communication with the transmitter covering the exterior of the vehicle is disabled. In this case, an event can take place in which the vehicle is left in a place in the condition where the auto-lock function is not executed and hence the vehicle doors are unlocked.